Alex Truesdell, who received a MacArthur “genius grant’’ for creating low-tech, affordable tools and furniture for kids with disabilities, returned to Lesley University — her alma mater — to meet with students and faculty. Truesdell, the founder and director of the nonprofit Adaptive Design Association, said people need to rethink their assumptions about disabilities. “We classify kids too quickly. . . . The assumption of capacity can set the bar way up,’’ said Truesdell, who worked at the Perkins School for the Blind for 19 years before founding ADA. She’s among 24 people in the country chosen as 2015 MacArthur Fellows, including journalist Ta-Nehisi Coates, Harvard’s urban sociologist Matthew Desmond, and MIT economist Heidi Williams.